I'd like to start with some of the projects which are currently U/C. In my opinion, most of them are not worth it, but what the hell, this is general overview of the development in the city and not personal "top-list", so here we go...

Yup, both were empty already for some time. Place, where the hotel will be built, was famous as the local strret art hub, while on http://goo.gl/maps/dtx6T, where Quadrio was built was nothing but an ugly communist square.

By the way, on the map I can see "Břevnovská radiála". What is planned there? An upgrade onto some kind of the urban motorway?

It's not an upgrade of Karlovarská/Bělohorská street as you probably think but a new urban motorway (connecting Prague's Outer Ring and Inner City Ring) in a new route, partly in tunnels. But for now, that project seems to be dead.